A number of pool cleaning systems have been devised utilizing strategically placed pop-up nozzles which are intermittently supplied with pressurized water. In repose, or inactive, each nozzle is retracted into a body so that its top surface is flush with the pool surface. When activated with pressurized water the nozzle rises above the pool surface and directs a stream of water across the surface to dislodge deleterious material from the surface and place it in suspension so it can be removed by the pool filter. Typically, such nozzles are caused to rotate a small amount about their axes with each activation so that a different area of pool surface is swept with each activation.
U.S. Pat. No. 4,322,860, granted Apr. 6, 1982 to Henry D. Gould for "Pool Cleaning Head with Rotary Pop-Up Jet Producing Elements" discloses such a pop-up nozzle. The mechanism for retracting and rotating the Gould nozzle employs a spring and cams and cam followers which are susceptible to breakage in use.
The same lack of reliability can be attributed to the nozzles disclosed in U.S. Pat. No. 4,371,994 granted Feb. 8, 1983 to Lester R. Mathews for "Rotational Indexing Nozzle Arrangement", and U.S. Pat. No. 5,251,343, granted Oct. 12, 1993 to John M. Goettl for "Swimming Pool Pop-Up Fitting".
Somewhat simpler nozzles are disclosed in U.S. Pat. No. 4,391,005 granted Jul. 5, 1983 to John M. Goettl for "Apparatus for Cleaning Swimming Pools", U.S. Pat. No. 4,792,095 granted Dec. 20, 1988 to Paul J. Pristo et al. for "Buffered, Fluid Dispensing Nozzle Unit", and U.S. Pat. No. 4,939,797 granted Jul. 10, 1990 to John M. Goettl for "Water Delivery Assembly for Cleaning Swimming Pools". All of the nozzles disclosed in these patents rely on metal weights to retract the nozzle. However, these nozzles are susceptible to jamming from debris and also there is the possibility of fatigue of plastic components.
There continues to be a need for a more reliable delivery system.